Local area networks (LANs) and switched media networks, providing services similar to LANs, are well known in the art. TCP/IP networks are a particularly widely used type of network. Many LANs are TCP/IP based LANs. Local area networks in general and relevant aspects of TCP/IP in particular are described in the following publications:
Douglas Comer, Internetworking with TCP/IP, second edition, vols. I-III, Prentice Hall, 1992-1993;
Wiener Feibel, Novell's Complete Encyclopedia of Networking, Novell Press, 1995;
Marshall Rose, The Open Book: A Practical Presentation on OSI, Prentice Hall, 1990;
Internetworking Standard for Bridging, IEEE 802.1 (D), IEEE, 1991;
Fred J. McClimans, "Taking Stock of Lan Switching", Business Communication Review magazine, April 1995;
Stephen Saunders, "Traffic Jam at the LAN Switch", Data Communications magazine, Nov. 21, 1994;
"NBMA Next Hop Resolution Protocol (NHRP)", Work in Progress, Dave Katz, David Piscitello, Bruce Cole, and James V. Luciani, available over the Internet from, for example, the IETF home page at www.ietf.cnri.reston.va.us.; and
the following Internet RFC documents, which are available over the Internet from, for example, the IETF home page at www.ietf.cnri.reston.va.us: RFC 791 ("Internet Protocol"); RFC 826 ("Address Resolution Protocol"); RFC 792 ("Internet Control Messaging Protocol"); RFC 1122 ("Requirements for Internet hosts--communication layers"); and RFC 1812 ("Requirements for IP Version 4 Routers").
A LAN may be subdivided into a plurality of networks. Typically, such a LAN uses the TCP/IP protocol and each of the plurality of networks is therefore an IP network. In a switched media network, hosts connected to a switched media may be assigned to a plurality of virtual networks. The term "network", as used throughout the present specification, refers to one of the one or more networks into which a LAN is subdivided, and may also be taken herein to include a "virtual network" within a switched media network. From the point of view of a station attached to the LAN and assigned to one of the networks, stations on another one of the networks are seen as being separate in the sense that direct communication with a station in another network is not allowed, even though the networks may be physically connected as part of the same LAN. Standard network protocols, such as TCP/IP, require that messages from a first station on a first network designated for a second station on a second network be sent via a router which is attached to both networks and which is responsible for routing messages between the two networks, even if the two stations are physically connected as pail of the same LAN. Alternatively, to a router which is attached to both networks, messages may be sent to a first router attached to the first network and then forwarded from the first router to one or more additional routers, eventually reaching a router which is attached to the second network.
When the first network and the second network are both networks within the same LAN or virtual networks belonging to the same switch, inefficiencies and overloading of the router may result as traffic which might be carried directly between the first station and the second station is actually sent via the router. Prior art systems fail to provide a satisfactory solution to these problems.
The disclosures of the above publications and of the publications cited therein are hereby incorporated by reference. The disclosures of all publications mentioned in this specification and of the publications cited therein are hereby incorporated by reference.